1. Field of the Invention
The present invention relates to a semiconductor module and, more particularly, to the semiconductor module wherein a cooling jacket, which conducts/radiates heat generated from the high-density packaged module, is mounted on a housing of this module to uniformly closely contact with the housing.
2. Description of the Prior Art
A semiconductor module containing one or more semiconductor devices is disclosed, for example, in Japanese Unexamined Patent Publication No. 59-213153. In a cooling apparatus disclosed in this publication, a heat conductive plate is placed in contact with the back surfaces of semiconductor chips, and a cooling board having cooling fluid flowing channels formed therein is then placed on this heat conductive plate, so that heat generated from the semiconductor chips is conducted through the heat conductive plate to the cooling board where the heat is absorbed and radiated by the cooling fluid. In this case, the cooling board is detachably mounted on the heat conductive plate by screw fasteners.
In Japanese Unexamined Patent Publication No 60-198848, a cooling apparatus is proposed wherein a mount housing includes a heat-radiating covering within which cooling fluid flowing channels are formed, such a covering being placed in contact with semiconductor chips on a substrate, and a spring to cause this heat-radiating covering to be tightenedly connected with the semiconductor chips.
In the above-mentioned Japanese Unexamined Patent Publication No. 59-213153 a cooling jacket or cooling board is mechanically fixed by the four screw fasteners onto the heat conductive plate which is a ceiling board of a module housing. Moreover, module structural members such as a flange to build up a number of the semiconductor chips, the housing with the heat conductive plate and the cooling board described previously are all joined mechanically and rigidly by screw fasteners. In such an arrangement for conducting and radiating the heat generated from the contacted semiconductor chips, because this contact condition between the cooling board and the heat conductive plate has a great influence on the cooling efficiency, it is inevitable for these structural members must be securely interconnected by the screw fasteners. Such secure screw-fastening does not give any trouble to the module housing of metallic material, but when brittle material, e.g., light-weighted non-metallic material is used for decreasing the weight of the module as required according to increase of the size, there is caused a problem that the module structural members are cracked by the screw-fastening. Furthermore, since packaging space is reduced due to the high-density packaging, the module structural members are fused by soldering or the like. In this case, the strong screw-fastening interferes heat deformation of the module, with thermal stress concentrating at joined portions of the structural members, and consequently, the fused portions tend to be broken, although mechanically fastened portions have some allowance against the heat deformation.
Moreover, in the above mentioned Japanese Unexamined Patent Publication No. 60-198848,in order to avoid the use of a screw-fastening, the only spring provided within the mount housing serves to press the heat-radiating covering onto the circuit substrate with the semiconductor chips mounted thereon, but with such an arrangement it is difficult to control displacements and pressing force so that the heat-radiating covering cannot be suitably fitted t the surfaces of the semiconductor chips and occupy the gaps between the covering and the respective semiconductor chips. It is also difficult to control the pressing force, whose amount has been determined in assembling, in response to differences in size of the module structural members and environmental changes after assembling.